Molding apparatus for splicing electrical cable

ABSTRACT

A molding apparatus having upper and lower platens to which are attached upper and lower mold forms. The apparatus includes two guide pins and a threaded rod for moving the upper platen vertically without disturbing the alignment between the platens and thereby the mold forms. The upper platen is articulated to facilitate placing a cable within and removing the cable from a mold cavity. Threaded fasteners are provided for distributing the clamping force on the upper platen necessary to provide a tight engagement of the mold forms. An injection apparatus communicates with the mold cavity for injecting additional molding material and for increasing pressure within the mold cavity. Bleed or vent openings in the upper platen and mold form are provided for allowing entrapped air to escape. Such a molding apparatus enables highly reliable splices of righ voltage cable to be accomplished easily and simply.

1 MOLDING APPARATUS FOR SPLlClNG ELECTRICAL CABLE [75] Inventor: ArthurL. Nelson, La Jolla, Calif.

[73] Assignee: Townsend and Townsend, San

Francisco, Calif.

[22] Filed: Feb. 20. 1973 [21] Appl. No.: 334,103

Related [1.5. Application Data [62] Division of Ser. No. 119.150, Feb.26. I971,

abandoned.

[52] US. Cl 425/108; 425/242; 425/450 C; 425/D1G. 802; 425/D1G. 812 [51]Int. Cl. B29c 27/14 [58] Field of Search 425/108, 450, 242, 243,425/384, 392, 812, 802. 203; 249/95 56] References Cited UNlTED STATESPATENTS 756,457 4/1904 Bent 425/242 [949.275 2/1934 Heintz 425/802 X2.319.372 5/1943 Tilton 1 425/108 2.407 683 9/1946 Prentice 1 t. 425/802X 2.7l6,623 8/1955 Tator t 249/95 X 2354.586 10/1960 Wacker 1. 425/812 X.95 Power .iource 7 tags? a 5 a? Q s 104 a e I I4 9 1 Apr. 29, 19753,148,430 9/1964 Hanner 425/812 X Primary Examiner-Francis S. HusarAssistant Examiner-David B. Smith Attorney, Agent, or Firm--Townsend andTownsend [57] ABSTRACT A molding apparatus having upper and lowerplatens to which are attached upper and lower mold forms. The apparatusincludes two guide pins and a threaded rod for moving the upper platenvertically without disturbing the alignment between the platens andthereby the mold forms. The upper platen is articulated to facilitateplacing a cable within and removing the cable from a mold cavity.Threaded fasteners are provided for distributing the clamping force onthe upper platen necessary to provide a tight engagement of the moldforms. An injection apparatus communicates with the mold cavity forinjecting additional molding material and for increasing pressure withinthe mold cavity. Bleed or vent openings in the upper platen and moldform are provided for allowing entrapped air to escape. Such a moldingapparatus enables highly reliable splices of righ voltage cable to beaccomplished easily and simply.

2 Claims, 11 Drawing Figures MOLDING APPARATUS FOR SPLICING ELECTRICALCABLE This is a division of application Ser. No. ll9,l50, filed 2/26/71,now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the invention The presentinvention relates to a molding apparatus and, more particularly, to animproved molding apparatus, especially for splicing high voltageelectrical cable in a reliable and efficient manner.

2. Description of the Prior Art Relatively low voltage electrical cablegenerally consists of one or more centrally disposed electricallyconductive cores or wires surrounded by a layer of electricallyinsulative material. Primarily, the insulative material is to protectagainst electrical shock and against short circuiting. At times itbecomes necessary to connect another segment of electrical cable to anexisting cable; this is commonly referred to as a splice." For lowvoltage cable, often splicing simply entails connecting the conductivecores together and covering the cores with insulative material, such asinsulative tape.

With the ever increasing requirements for more power, higher and highervoltages are being transmitted along electrical cables; of these,underground cables require reliable insulation. For many years oilfilledcables fulfilled the insulation requirements. However, oil-filled cablesare expensive to manufacture, to install and to maintain. In recentyears, high voltage cables having solid dielectric materials have beendeveloped. These materials include polyethylene, crosslinkedpolyethylene and ethylene propylene rubber. Using these materials, somecables have been designed to transmit voltages as high as 138 kilovolts.High voltage cables, however, present some difficult problems whencompared to low voltage cables since there is a far greater propensityfor failure due to a short circuit. Should there be an imperfection inthe high voltage cable's conductive core, an excess charge will build upat the imperfection and create a corona discharge; that is, there willbe a discharge through the insulative material into the surroundingenvironment. The imperfection is more generally referred to as adiscontinuity." For example, if a copper wire is used as theelectrically conductive core, any burr or scratch on the wire surfacewill serve as a discontinuity and initiate a corona discharge. Such adischarge is usually fatal to the cable since there will be aprogressively increasing amount of dielectric stress generated in theinsulative material until failure occurs.

One method for solving the problem of corona discharge is to provide alayer of semi-conductive material about the conductive core. Thissemi-conductive layer may be partially of synthetic resin which willallow it to be molded about the conductive core so as to present arelatively smooth outer surface along which the high voltage charge willtravel. Splicing high voltage cable however is very difficult since anydiscontinuity introduced by the splicing process may engender a coronadischarge. One common problem is the introduction of entrapped air; theentrapped air forms a discontinuity and may cause a corona discharge.Two basic requirements for a reliable high-voltage splice are, first,that the added insulative material be compatible with the originalinsulative material and, second, the added insulative material have adielectric constant similar to the dielectric constant of the originalmaterial. To be otherwise risks the creation of a discontinuity orelectrical interface" along which ionization may take place or water mayenter. In the high voltage hand-taped splices, an attempt is made tominimize this effect by making long tapers, that is pencilling" thecable insulative material prior to splicing to increase the length of apotential ionization path.

In addition to the technical problems involved, any system developed toprevent discontinuities during splicing should be a relativelyeconomical one. For example, excessively high labor costs, such as thoserequired when a highly specialized talent is necessary to operate thesystem, or any system which is not adaptable to portable field usagewill never meet the requirements deemed necessary.

A traditional method for splicing low voltage cables using a moldingdevice required the spliced section to be covered with an excessiveamount of electrically insulative unvulcanized material usually in tapeform. Next, the mold would be placed around the spliced area and heatand pressure applied; however, because of over packing, the moldingdevice could not be fully closed thereby allowing the unvulcanizedmaterial to flow outwardly between the mold halves. This movement from ahigh pressure region to a low pressure region created a tension force onthe conductive core causing the core to move. A misalignment due to themovement presents little problem for low voltage cables; but such amisalignment could present major problems for high voltage cables bycreating discontinuities, and in some cases prevent the conductive corefrom receiving a complete covering of insulative material. The moldingdevice also tended to entrap air which is inevitably included with eachturn of the unvulcanized insulative tape. There is no egress throughwhich this entrapped air may escape. Once again, the effect on highvoltage cables of entrapped air is far different than the effect on lowvoltage cables. Hence, such a molding device is not suitable for highvoltage splicing.

Another splicing technique for low voltage cables consisted simply ofhand taping insulative material about the conductive core. While resultsfor low voltage cables were satisfactory, problems and expense increasedas the technique was applied to higher voltage cables. First, it becamenecessary to make long pencils" or tapers prior to splicing to increasethe potential ionization path thereby lessening the chance of a pathdeveloping; second, the taping process was time consuming, laborious andgave unreliable results. A newer system developed for higher voltagecables comprised the use of a plastic mold placed about the splicedsection to act as a container for a liquid insulative material which isthen poured into the mold. Since neither sufficient heat or pressure isused, bonding is totally unreliable so that water leakage is enhanced,and the likelihood of air bubble discontinuities is great. As mentioned,water leakage or air bubbles will cause a short circuit and failure ofthe cable.

Still another method developed for high voltage cables comprisedwrapping insulative tape about the splice, covering this tape with amylar tape and surrounding the splice with steel bands. Next, heatingblankets were applied in an attempt to fuse the insulative tape.Problems with this method included long time periods to accomplish, onthe order of i2 hours,

extreme expense, the inevitable inclusion of air bubbles and aninability to function with some types of insulative materials such aselastomers.

SUMMARY OF THE INVENTION The present invention solves the abovementionedproblems while achieving an economically feasible system by providing amolding apparatus comprising first and second mold forms movable betweenopen and closed positions and forming a mold cavity; means engaging saidfirst and second mold forms for retaining said mold forms in said closedposition; means in thermal communication with the mold forms forsupplying heat to the mold cavity; and means formed in said mold formsfor communicating said mold cavity and the environment. The inventionfurther includes a material injection apparatus for the molding systemcomprising a housing having an interior space and first and second openends, the interior space communicating with the mold cavity through thefirst open end; and means movable within the housing interior space forcausing material to be moved from the housing interior space to the moldcavity and for allowing gas within said interior space to vent to theenvironment. The inventive method for splicing high voltage electricalcable comprises the steps of providing exposed electrically conductiveelements; joining the exposed elements; cover ing the joined elementswith a smooth, semi-conductive material; providing insulative material;covering the semi-conductive material with the insulative material;providing mold forms forming a mold cavity; placing the cable within themold cavity; applying heat to the mold cavity; and selectively allowingheated insulative material to escape from said mold cavity.

It is the general aim of the present invention to provide a moldingapparatus for producing superior and reliable splices of electricalcables quickly. simply and at relatively low cost.

Another aspect of the present invention is to provide a moldingapparatus which allows the introduction of extra molding material to themold cavity after the mold is closed and which allows air or other gasesto escape from the mold cavity to insure a reliable splice.

Another object is to provide a molding apparatus which is simplyconstructed and easily operated. The apparatus is flexible toaccommodate many different size mold forms and is easily opened andclosed without upsetting alignment of the mold forms.

Yet another object of the present invention is to provide a moldingapparatus which is small enough to be portable yet does not over stressthe apparatus platens when applying pressure to the mold forms.

Another aim of the present invention is to provide a molding apparatuswhich selectively vents gas from the mold cavity to the environment andwhich allows heated molding material to escape thereby indicating theprogression of the molding process.

Other objects and advantages of the invention will appear from thefollowing description taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. la is a plan view of two cablesegments which have been prepared for splicing.

FIG. lb is a plan view of the cable segments of FIG. in after splicinghas been completed.

FIG. 2 is a perspective view of an embodiment of the molding apparatusof the present invention in a closed position.

FIG. 3 is a perspective view of the molding apparatus in an openedposition.

FIG. 4 is an enlarged plan view of the upper platen of the moldingapparatus.

FIG. 5 is a sectional elevational view taken along line 55 of FIG. 4.

FIG. 6 is an enlarged elevational view, partly in cross section, of athreaded rod engaging upper and lower platens of the molding apparatus.

FIG. 7 is an enlarged elevational view, partly in cross section, takengenerally along the line 77 of FIG. 2.

FIG. 8 is an enlarged partial plan view of the upper platen similar tothat shown in FIG. 4 for illustrating the adjustable openings of theupper platen.

FIG. 9 is an enlarged sectional view of mold forms taken through line9--9 of FIG. 2.

FIG. 10 is an exploded perspective view of a taped cable and a premoldedboot.

DESCRIPTION OF THE PREFERRED EMBODIMENT While the present invention issusceptible of various modifications and alternative construction, anillustrative embodiment is shown in the drawings and will herein bedescribed in detail. It should be understood, however, that it is notthe intention to limit the invention to the particular form disclosed;but. on the contrary, the intention is to cover all modifications,equivalences and alternative constructions falling within the spirit andscope of the invention as expressed in the appended claims.

Referring now to FIGS. la and 1b, there is illustrated a firstelectrical cable segment 10 which is to be spliced to a secondelectrical cable segment 12. Generally, a high voltage electrical cableincludes an electrically conductive central core, such as a strand ofelectrically conductive wire l4, 14' around which is a semiconductivematerial, such as ethylene propylene rubber containing lampback l6, 16'.The semiconductive material is surrounded by a layer 18 of electricallyinsulative material such as polyethylene, crosslinked polyethylene orethylene propylene rubber. Surrounding the electrically insulative layerI8 is an electrical shield 20, 20'. The splice is preferably made byjoining the stranded electrically conductive wire 14, 14' in anyconvenient way, such as by crimping within a joining sleeve, or by usinga material which when ignited generates a great deal of heat. The jointis then filed smooth. Next. a semi-conductive material is placed aboutthe conductive wire and wrapped or molded so as to achieve a reasonablysmooth outer surface 22. Finally, the spliced portion is wrapped with anelectrically insulative material such as unvulcanized ethylene propylenerubber. A shield segment is placed within the wrapping connected to theshields 20, 20' to achieve a single shield 20". The wrapped cable isthen placed in a mold cavity where heat and pressure are applied toprovide a smooth, securely bonded spliced region. It is to be understoodthat various electrically insulative materials may be used with themolding apparatus to be described and that what occurs during themolding process is a function of the material used. For example, whenpolyethylene is molded, it simply flows and reforms to the shape of themold. Cross-linked polyethylene reforms and undergoes a chemical changewhen heated as does ethylene propylene rubber. ln any case. theinsulative material is usually applied to the cable in a tape form;after molding it is desired that the added insulative material besecurely bonded to the original insulative material and have therequisite electrical and mechanical characteristics.

As discussed, splicing of high voltage cable in the prior art requiredthat initially the layers of the segments above the conductive wire havea gradual pencillike taper. The added materials were then carefullytaped by hand in a slow, careful manner to establish as good a bond orconnection as possible to the conductive wire and existing layers so asto minimize entrapped air. The tape also had to conform closely to themold cavity that was to be used. But, it was desirable to wrap the tapeto a slightly oversized condition so as to force out air or other gaswithin the splice when the mold applied heat and pressure. However. byforming an oversized cable, the mold could not be completely closed;this created a pressure differential through the opening between themold halves. Hence, an inherent dilemma developed--trapped air ormisalignment problems. Proper molding required a high degree of skillsince once heat and pressure were applied. there would be a tendency forthe material around the conductive wires to flow outwardly through theopening between the mold halves placing tension on and causingmisalignment of the conductive wires. As mentioned, this tensionincreased the likelihood of damage to the conductive wire which raisedthe likelihood of a discontinuity and the eventual failure of the cablerequiring a new splice attempt. Any effort to avoid this problem byplacing less insulative material about the cable tended to increase thechance of entrapped air which also had the effect of creating adiscontinuity and eventual failure ofthe cable. To strike a balancerequired a high degree of skill and excessive time, thus, driving costsup.

An important aspect of the present invention is the provision of amolding apparatus which is simply constructed and easily operated toobviate the need of highly skilled labor and excessive time. Theapparatus is also portable to allow convenient field usage. Referringnow to FIG. 2 and 3, the molding apparatus of the present inventioncomprises an upper platen 40, a lower platen 42 and upper and lower moldforms 44 and 46. The upper platen 40 is articulated by two hinges 48 and50 so as to allow a portion of the upper platen to be rotated about thehinges without misaligning the upper platen and the lower platen.Precise vertical movement of the upper platen relative the lower platenis achieved by the two guide pins 52 and 54. Vertical movement iscontrolled by the use of a threaded rod 56 within a threaded opening 58of the upper platen and operable by a removable handle 60. The threadedrod is also rotatably received by the lower platen 42.

Connected to a front peripheral surface 70 of the upper platen is ahandle 72 for conveniently rotating the upper platen. Rotatably mountedwithin two recesses 80 and 82 in a front peripheral surface 74 of thelower platen are two threaded fasteners 76 and 78. The fasteners canrotate from a position generally parallel to the lower platen. as shownin FIG. 3, to a position generally perpendicular to the lower platen, asshown in FIG. 2, disposed within recesses 84 and 86. respectively, inthe front peripheral surface 70. Positioned to the rear of the moldingapparatus is a control box 86 having a control switch 90 and twoindicator lights 92 and 94 for indicating to an operator when power isbeing delivered from a power source 95 to the upper and lower platensrespectively. Power cords 96 and 98 lead from the control box 86 to theupper and lower platens, respectively, and connect to cartridge heaters97 and 99, P16. 4, which are positioned within the upper and lowerplatens. Strip heaters may be used in the alternative. The temperatureof each of the platens is controlled by control knobs 100 and 102 of theupper and lower platens, respectively, and are moved in response totemperature indications provided by thermometers 104 and 106. Thecontrol box 86 is detachable and pivotable to allow usage in tightspaces such as within manholes, for example. By detaching, a smallerwidth of the apparatus is achieved. Mounted atop the upper platen is amaterial injection apparatus 108 which is in communication with the moldcavity formed by the mold forms 44 and 46.

It is a major aspect of the present invention to provide a moldingapparatus which is easy to open and close without upsetting a precisealignment of the upper and lower platens and mold forms. In addition, itis an important advantage of the present invention to provide thefacilitated opening and closing while preventing excessive stressconcentrations on the platens when the platens are in their closedpositions. Still further, it is an aspect of the present invention toprovide a molding apparatus with which a variety of mold forms havingdifferent mold cavity sizes can be used.

Referring now to FIGS. 4, 5, 6 and 7, there is illustrated in moredetail the upper platen 40 which is articulated and comprised of aforward rotatable portion 110 and a rearward vertically translatableportion 112. The rear portion 112 has three openings, openings 114 and116 to receive the guide pins 52 and 54 and the threaded opening 58 toreceive the threaded rod 56. The guide pins are fixed to the lowerplaten. so that the upper platen is able to move in a vertical directionwithout changing position in a horizontal plane relative the lowerplaten. Thus, the insertion and removal of a cable does not requirealignment adjustments. Insertion and removal of cables are facilitatedby having the front portion 110 of the upper platen selectivelyrotatable relative the rear portion 112 between open and closedpositions. This is accomplished with the relatively simply constructedhinges 48 and 50. For exam ple, the hinge 50 includes a shaft 116positioned within an opening 118 in a leg 120 of the rear platenportion. The shaft 116 also extends into the front platen portion. Thefront platen portion is allowed to rotate relative the rear platenportion to a limited extent due to the shape of an outer surface of theleg 120, FIG. 4, which includes an upper rounded portion 122, FIG. 5,and a flat abutment portion 124. The abutment portion abuts a rearsurface 126 of the front platen portion to limit the motion of the frontplaten portion to an aligned closed position as shown in FIG. 5 in solidline, while the round portion 122 allows the front platen portion torotate to a perpendicular open position, as shown in phantom line inFIG. 5.

The forward portion of the upper platen also includes two parallelseries of openings such as the series including the opening 130 and theseries including the opening 132. These openings align with openings inthe mold form 44, such as the openings 130a and 134 as shown in FIG. 7.and receive threaded fasteners such as the screw 136 to securely fastenthe upper mold form to the upper platen. In a similar fashion. openings.such as the opening 138. are provided in the lower platen to align withopenings. such as the opening I40. in the lower mold form 46 forreceiving fasteners such as the screw I42 to securely fasten the lowermold form to the lower platen. The lower platen and attached lower moldform are relatively stationary. while the upper platen and attachedupper mold form are movable between open and closed positions asdescribed with reference to FIG. 5. Thus. the platens and the mold formsare in an open position. as shown in FIG. 3. to receive a wrapped spliceand to allow removal of a molded splice. and in a closed position asshown in FIG. 2 during the molding process.

As mentioned hereinabove. to close the platens and the mold forms. it issimply necessary to rotate the forward portion I10 to an alignedposition with the rearward portion II2. Then. the handle 60. FIG. I,attached to the threaded rod 56 is rotated to cause the upper mold formto move into engagement with the lower mold form. To prevent cabledamage by distortion of the conductive wire. it is very desirable tohave a tight fitting. precisely aligned engagement between the upper andlower mold forms so that during the molding process there is no leakagealong the region where the mold forms come together, commonly re ferredto as the parting line, nor is there any shifting of the cable withinthe mold cavity. Since the force causing the upward and downwardmovement of the upper platen occurs at the threaded opening 58 which isadjacent a rear peripheral edge 150, FIG. 4. excessive stressconcentrations in the upper platen are avoided by having the threadedfasteners 76 and 78 engage the forward portion of the upper platen.Attached to the threaded fasteners are nuts I52 and I54 which may betightened to bear against washers 156, 158. respectively. Thus. downwardforces applied to the upper platen are located at three triangularlydisposed loca tions. adjacent the threaded rod 58, adjacent the threadedfastener 76 and adjacent the threaded fastener 78. to achieve a moreeven distribution. The even distribution or forces on the platensubstantially reduces or eliminates breakage of the upper platen andassures a tight engagement of the upper and lower mold forms.

Another important aspect of the present invention is a provision forallowing the injection of additional material into the mold cavity oncethe mold forms have been secured in their closed position. One of themajor disadvantages of the prior art is overcome since it is no longernecessary to "over pack" the mold cavity. In ad dition. the apparatusfor injecting the additional mate rial allows for the escape of gas.usually air. that may have become entrapped. Still another advantage isthat the injecting apparatus provides a controlled way of increasing thepressure within the mold cavity. Referring now to FIGS. 4 and 7, thereis illustrated a material in' jection apparatus 160 comprising acylindrically shaped housing I62 having an interior space I64 and apiston 166 which is movable vertically within the interior space 164 bythe rotation of a threaded rod I68 which is connected to the piston andsupported by a cap nut I70 having a threaded opening 17] to receive thethreaded rod and a threaded recess 173 to receive a threaded upperportion 175 of the housing. The

threaded rod has an opening I74 in its upper portion to receive acrossrod 176 to facilitate the hand rotation of the rod I68 and thereby thevertical movement of the piston. A threaded extension I78 is integralwith the housing 162 and extends within an opening ISO in the upperplaten prmiding direct communication between the intcrior space 164 anda mold cavity 144 via a central opening I82 in the extension 178 and anopening I86 in the upper mold form 44. A slug I88 of insulative materialis placed within the interior space 164 and pushed into the mold cavityabout the wrapped cable 190.

Upon heating the platens. the material in the mold cavity and within theinjection apparatus will begin to soften. so that an operator may simplygrip the cross rod 176 and rotate it to cause additional material to beinjected into the mold cavity. It is to be noted that the piston 166 isof a smaller diameter than the diameter of the interior wall [92 of thehousing. This is done so that any air which is entrapped within theadditional material I88 may rise and escape through an annularpassageway I93 between the piston and the interior wall and through anopening I94 in the nut 170. In addition to the air escape offered by thematerial injection apparatus, there are a series of openings in theupper platen such as the opening 200. and a series of aligned openingsin the upper mold form such as the opening 202 which communicates themold cavity with the environment. The openings are spaced generallyalong the longitudinal length of the splice. as shown in FIG. 4, so asto offer convenient air escape routes.

As the operator rotates the piston downward. he will be given afeedback" as to the progression of the molding process since theresistance to downward movement of the piston will be a function of theheat input to the mold cavity. Referring now to FIG. 8. the alignedopenings through the upper platen and the upper mold form also serve asa feedback device to an operator to determine when enough heat andpressure have been applied to the splice. For example. once a majorportion of the gas which was entrapped within the mold cavity has beenexpelled. some of the heated and softened material in the mold cavitywill begin to sputter and ooze through the openings such as illustratedin conjunction with the opening 200b forming segments 201 and 203 and asnake-like filament 204 of material. These filaments also containentrapped air.

To provide even more control of the molding operation. small rotatabletabs such as the tab 206 adjacent the opening 200a are provided topartially or totally block a corresponding opening so as to allowlocalized increases in pressure along the longitudinal length of thesplice during the molding process. For example. tab 206b is illustratedpartially covering opening 2006. while the tab 206: is totally coveringthe opening 200d. Each of the tabs are pivoted about a pin. such as thepin 208 of the tab 206. and are easily hand rotated by the operator. Itis now apparent that a properly bonded splice can be achieved withoutthe usual fear of trapped air. without the need to spend excessive timecarefully tapering and then taping the splice. without the fear that thesplice may become distorted due to a leakage along the parting line ofthe mold forms and without the need to highly skilled personnel tooperate the molding apparatus.

When as shown in FIG. 2, it is necessary to use mold forms which arelonger than the corresponding dimension of the platen. It has been founddesirable to clamp the mold form ends so as to insure a tight engagementof the mold forms at their ends in addition to the tight engagementalong the central portion insured by the platens. One way of achievingthe tight engagement is to provide two elongated bolts 210 and 212, FIG.9, which are engaged respectively by nuts 214 and 216. These boltsadditionally have the effect of reducing the stress on the platens andtheir supporting members caused by the pressure within the mold.

In operation, an operator bears a small portion of the conductive wireof the cables to be spiced. welds the conductive wires together and thenapplies an insulative material to cover the wires, such as by having atape of a material identical to the insulative layer of the cable orcompatible with this layer so as to insure bonding. The material isapplied about the spliced region so as to fully cover the conductiveelements and be slightly undersized when compared with the mold cavityto be used. The molding apparatus is prepared by determining which sizemold forms to use and tightly securing each of the mold forms to theirrespective platens. The platens and the mold forms are then moved totheir opened positions to receive the wrapped cable and initiate themolding operation. It is noted as illustrated in FIG. 3 that the endportions of the mold forms may have internal serrations 220 to moresecurely grip the cables and prevent movement during the moldingoperation provided the insulative material used is one that will returnto a smooth outer surface when removed from the molding apparatus. Ithas been found desirable to wrap a layer of linen tape about the cableportions which contact the mold forms to allow the cable to expandduring the molding operation without injuring. to preserve pressurewithin the mold cavity and yet block the escape of the oozing insulativematerial, to protect the existing insulative covering from excessiveheat and to provide a porous opening during the initial portion of themolding operation to serve as another escape route for any entrappedgas.

The platens and mold forms are then moved to their closed position withthe threaded rod 56 being rotated to cause a tight engagement betweenthe upper and lower mold forms. The threaded fasteners 76 and 78 arethen moved into place (as shown in FIG. 2) and the washers 156 and 158caused to bear against the upper surface of the upper platen, so that areasonably even distribution of force is applied to the upper plateninsuring a tight closure of the mold forms. If the mold forms extendbeyond the platens, clamps may be provided, such as the boltnutcombinations of FIG. 9. Next, the control switch 90 is activated so asto energize the heating elements within the platen. The slug 188 ofadditional material is deposited into the injection apparatus 160 toawait heating.

Temperature control of the platens is made by a suitable setting of theknobs 100 and 102 with feedback to the operator being supplied by thethermometers 104 and 106. Once the unmolded tape material within themold cavity and within the injection apparatus has been heatedsufficiently enough to flow, the operator may begin lowering the pistonI66 to cause the additional insulative material to enter the moldcavity. As explained earlier, any entrapped gas is allowed to escapethrough the injection apparatus, through the aligned openings in theupper mold forms and the upper platen, and longitudinally through theends of the mold forms.

Meanwhile, pressure is created by the heating process and by theoperator forcing the additional material from the injection apparatusinto the mold cavity. By way of example when ethylene propylene rubber(EPR) is used as the insulative material, the cable is heated to about250 F to allow the EPR to flow and form in the shape of the mold cavity.The injection apparatus may then be removed and replaced with a threadplug (not shown) or kept in place, while the temperature of the cable israised to about 300 F to cure the material. Cure time is between 5 and30 minutes depending upon the material usedv The actual temperature ofthe platens depends upon the size of the cable, the mold forms and theconductive corev The operator will be able to gauge the progression ofthe molding operation by the resistance to the injection of the addedmaterial and by observing the openings 2.00. The length of the filamentscoming through the openings of the upper platen will also indicatewhether it is desirable to increase pressure locally along the splice bymoving a tab over its corresponding openings, as shown in FIG. 8. Byrestricting the opening, there will be a buildup of pressure in theregion of the mold cavity adjacent the opening thereby giving theoperator a great deal of flexibility in achieving a reliable bond.

If a semi-conductive material is used about the conductive wires, thenit may be necessary to perform the molding operation twice, first tobond the semiconductive material about the conductive core and second tobond the insulative material about the semiconductive material.

As an alternative to completely wrapping the insulative material aroundthe cable, a premolded boot may be used. Boots are simply insulativematerial premolded to the size and shape of the mold cavity. Referringto FIG. 10, a cable 300 has a partial wrap of insulative tape 302 placedaround it. A boot 306 having a hollow interior 308 and a longitudinalslit 310 is positioned about the wrapped portion. The conductiveelements are wrapped with only enough unvulcanized material to be a snugfit inside the bootv The slot is placed in an upward position in themold cavity so that the added material introduced by the injectionapparatus flows into the slot and fills the region within the boot. Theboot offers the advantage of saving wrapping time and, importantly,insures the concentricity of the conductive core since the premoldedboot acts as a precise spacer.

It is apparent that the present molding apparatus as is greatly superiorto the devices heretofore available. Not only are highly skilledtechnicians obviated, but highly reliable splices can be achieved withina relatively short period of time so as to establish a tremendouseconomic advantage.

For further purposes of illustration. the molding apparatus describedmay be used with many materials, the following are just a specific few:neoprene, rubber. ethylene propylene rubber, polyvinyl chloride,polyurethane, cross-linked polyethylene. silicone and polyethylene. Inaddition to splicing electrical cable, the molding apparatus may be usedto splice air hoses, make molded rubber parts and encapsulate electricalcomponents. One particular embodiment of a molding apparatus having anavailable molding area of 20 inches by 7 inches has a maximum powerrequirement of [.600 watts at l l5/230 volts and 50/50 Hz. The platensare capable ofa temperature range between l50 F to 420 F and approximatepreheat time is l3 minutes. By way of comparison to illustrate anotheradvantage of the present invention a typical conventional taped spliceof a 69 KV cable has a diameter of 5 inches and is about 48 inches long.A splice of the same cable made according to the trackings herein wouldhave a diame ter of 3 /8 inches and be about 13 inches long. Preferably.the platens and the mold forms are of aluminum alloy. so that the weightof the unit described is approximately 40 pounds. It is of course.understood that smaller molding apparatus may be constructed weighing aslittle as 12 pounds. It is to be understood that low voltage cables maybe reliably spliced with the appara tus described and that theinsulative material may be wrapped in tape form. boot form or sheet formfor ex ample. Additionally Y" and T splices can be easily achievedsimply by providing the proper mold forms. In the past. such spliceswere not performed because of the inability to hand tape a smooth,waterproof wrap at the corners of the Y" and T.

I claim: l. A molding apparatus comprising: first and second mold formsmoveable between open and closed positions and forming a mold cavity;means engaging said first and second mold forms by retaining said moldforms in said closed position; means in thermal communication with saidmold forms for supplying heat to said mold cavity; means formed in saidmold forms for communicating said mold cavity and the environment; meansconnected to said mold forms for supplying material to be molded and forincreasing pressure within said mold cavity, including a housing havingan interior space and first and second open end. said interior spacecommunicating with a mold cavity through said first open end and meansmoveable within said housing interior space for causing material to bemoved from said housing interior space to said mold cavity and forallowing gas within said interior space to vent to the environment; saidretaining means including first and second platens; a guide pin foraligning said first and second mold forms in said closed position; athreaded rod attached to said second platen and engaging said firstplaten through a threaded opening for bringing said mold forms intotight engagement; and a threaded fastener mounted to said second platenand engaged by said first platen along a portion spaced form the portionengaged by said threaded rod; and including:

a hinge dividing portions of said first platen. a first portion beingmoveable between open and closed positions corresponding to the open andclosed positions of said mold forms;

openings in each of said first and second platens for corresponding toopenings in said first and second mold forms whereby fasteners arereceived to attach said platens and said mold forms;

additional openings in said first platen and additional aligned openingsin said first mold form for allowing gas in said mold cavity to escape;

means connected to said first platen for selectively blocking saidadditional openings of said first platen.

2. A molding apparatus comprising: first and second mold forms moveablebetween open and closed positions and forming a mold cavity; meansengaging the first and second mold forms for retaining the forms intheir closed positions, the retaining means including first and secondplatens, a guide pin for aligning the first and second mold forms in theclosed position, a threaded rod attached to the second platen and engaging the first platen through a threaded opening for bringing the moldforms into tight engagement, a threaded fastener mounted to the secondplaten and engaged by the first platen along a portion spaced from theengaged by the threaded rod; a hinge dividing portions of the firstplaten. a first portion being moveable between open and closed positionscorresponding to the open and closed positions of the mold forms; eachof the platens and of the mold forms including corresponding, alignedopenings; fasteners received in said openings and attaching the platensto the respective mold forms; means in thermal communication with themold forms for supplying heat to the mold cavity; means for supplyingmaterial to be molded to the mold cavity and for increasing the pressurewithin the cavity; at least one of the forms and of the correspondidngplaten including a plurality of aligned openings communicating the moldcavity with the atmosphere for allowing gas and pressurized materialsupplied to the cavity to escape thereform to the atmosphere; and meansconnected to the last mentioned platen for selectively blocking theapertures.

1. A molding apparatus comprising: first and second mold forms moveablebetween open and closed positions and forming a mold cavity; meansengaging said first and second mold forms by retaining said mold formsin said closed position; means in thermal communication with said moldforms for supplying heat to said mold cavity; means formed in said moldforms for communicating said mold cavity and the environment; meansconnected to said mold forms for supplying material to be molded and forincreasing pressure within said mold cavity, including a housing havingan interior space and first and second open end, said interior spacecommunicating with a mold cavity through said first open end and meansmoveable within said housing interior space for causing material to bemoved from said housing interior space to said mold cavity and forallowing gas within said interior space to vent to the environment; saidretaining means including first and second platens; a guide pin foraligning said first and second mold forms in said closed position; athreaded rod attached to said second platen and engaging said firstplaten through a threaded opening for bringing said mold forms intotight engagement; and a threaded fastener mounted to said second platenand engaged by said first platen along a portion spaced form the portionengaged by said threaded rod; and including: a hinge dividing portionsof said first platen, a first portion being moveable between open andclosed positions corresponding to the open and closed positions of saidmold forms; openings in each of said first and second platens forcorresponding to openings in said first and second mold forms wherebyfasteners are received to attach said platens and said mold forms;additional openings in said first platen and additional aligned openingsin said first mold form for allowing gas in said mold cavity to escape;means connected to said first platen for selectively blocking saidadditional openings of said first platen.
 2. A molding apparatuscomprising: first and second mold forms moveable between open and closedpositions and forming a mold cavity; means engaging the first and secondmold forms for retaining the forms in their closed positions, theretaining means including first and second platens, a guide pin foraligning the first and second mold forms in the closed position, athreaded rod attached to the second platen and engaging the first platenthrough a threaded opening for bringing the mold forms into tightengagement, a threaded fastener mounted to the second platen and engagedby the first platen along a portion spaced from the engaged by thethreaded rod; a hinge dividing portions of the first platen, a firstportion being moveable between open and closed positions correspondingto the open and closed positions of the mold forms; each of the platensand of the mold forms including corresponding, aligned openings;fasteners received in said openings and attaching the platens to therespective mold forms; means in thermal communication with the moldforms for supplying heat to the mold cavity; means for supplyingmaterial to be molded to the mold cavity and for increasing the pressurewithin the cavity; at least one of the forms and of the correspondidngplaten including a plurality of aligned openings communicating the moldcavity with the atmosphere for allowing gas and pressurized materialsupplied to the cavity to escape thereform to the atmosphere; and meansconnected to the last mentioned platen for selectively blocking theapertures.